#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxn = 110;
struct node
{
	int a;
	int b;
}q[maxn];
int main()
{
	int t;
	cin>>t;
	while(t--)
	{
		int flag = 0;
		int n;
		cin>>n;
		for(int i = 0;i<n;i++)
		{
			cin>>q[i].a>>q[i].b;
		}
		for(int i = 0;i<n;i++)
		{
			if(q[i].a<q[i].b) 
			{
			//	printf("****\n");
				
				flag = 1;
				break;
			}
			if(i!=0&&(q[i].a<-q[i-1].a||q[i].b>q[i-1].b+(q[i].a-q[i-1].a)||q[i].b<q[i-1].b))
			{
				//printf("****\n");
				flag = 1;
				break;
			}
		}
		if(flag) cout<<"NO"<<endl;
		else cout<<"YES"<<endl;
	}
} 
